JPH10281952A - Rapid analysis by laser of molten steel component and laser analyzing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate an adverse effect of CO gas by irradiating laser to molten steel, vaporizing a part of it for particulates, carrying it to a cell with inert gas, separating carrier gas including particulates and CO gas, and analyzing the particulates. SOLUTION: A probe 3 fitted on a water-cooled sub-lance 11 is brought near the surface of molten steel 4. The laser beam of a laser 1 for generating particulates is irradiated to the molten steel 4 through a condensing lens 2 to shut off inside and outside gas with the quartz glass 21 of the probe 3. Inert gas is put in the probe 3 from a gas inflow tube 5, and the particulates of steel generated with laser irradiation is carried to a cell 8 from a gas discharging tube 6 together with CO gas diffused from the molten steel 4. After gas including particulates is passed through a filter 82 fitted on the cell 8 for a fixed time, it is converted into gas not including CO gas to separate and remove CO gas near the particulates deposited on the filter 82. Ar gas is then sprayed over the filter 82 to float the particulates and carry it to a plasma analyzing device 9 for C-analysis of the particulates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for rapidly analyzing the content of components in molten steel, for example, carbon, manganese, phosphorus, sulfur, etc., in steelmaking work in a converter or the like.

[0002]

2. Description of the Related Art Recent steelmaking methods, particularly steel refining methods using a converter, have become the mainstream of steelmaking methods worldwide due to their high productivity and speed. In this converter steelmaking method, oxygen is blown into hot metal housed in a converter, and carbon (hereinafter referred to as C), manganese (hereinafter referred to as Mn), phosphorus (hereinafter referred to as P), sulfur (hereinafter referred to as S) Etc.) to produce steel, and by blowing oxygen for about 10 minutes, the C content of 4 wt% or more in the hot metal before blowing is reduced to about 0 in accordance with the use of the steel. The C content is in the range of 0.01 to 1 wt%.

[0003] Since properties such as strength of steel greatly depend on the C content, the allowable range of the C content is as severe as ± 0.01 wt% or less. For this reason, it is strongly demanded to quickly obtain the component composition of molten steel, for example, the C content during blowing.

Conventionally, as shown in FIG. 5, high-energy and high-purity oxygen gas is supplied from the tip of an oxygen lance 43 during blowing in a converter 40, and the molten steel 4 and the slag 41 are stirred by the oxygen gas. , Causing a rapid reaction. The decarburization reaction of the molten iron is a kind of gas-molten steel reaction, and the rapid reaction changes the component composition of the molten steel 4, particularly, the C content during blowing. Therefore, in order to obtain the changing C content, various measuring devices are installed on the sublance 11,
Some measures have been taken such as inserting it into the furnace of the converter 40 to obtain the composition of the molten steel 4 (for example, Iron and Steel Handbook, 3rd edition, 2nd edition).
Winding, iron and steel making, p. 490 (1979, edited by the Iron and Steel Institute of Japan).

In the conventional rapid analysis of steel during blowing, there is a method of estimating the C content from the solidification temperature of the steel, but errors tend to occur. Further, there is a method in which the molten steel 4 is sampled from a probe at the tip of the sub-lance 11, cooled, cut and polished, and the polished surface is subjected to emission analysis to measure the component composition of the molten steel 4.

However, in this method, it takes about three minutes from the start of sampling until the analysis result is obtained.
In a converter operation in which blowing is performed about 40 times in 24 hours (one day), the average blowing time per blow is about 36 minutes.
If the time of about 3 minutes until the analysis result comes out after the end of blowing, the productivity is about 8% (= (3 minutes / 36 minutes) × 1).
00) will be improved.

[0007] Further, about 3 minutes before the end of the blowing, the molten steel 4 is sampled, cooled, cut and polished, and the polished surface is subjected to luminescence analysis to obtain an analysis result for about 3 minutes. There is a method of completing such an analysis operation during the blowing time.

However, in this method, the blowing is continued and the composition of the molten steel 4 changes during about 3 minutes when the analysis operation is performed. Further, the accuracy of the estimated molten steel composition obtained by estimating the change of the molten steel composition from the analysis value is low. In some cases, after the blowing, a process of “post-blowing” must be performed to correct errors in the analysis results.

[0009] This "post-blowing" is performed by using molten steel 4
However, it is very important to obtain molten steel composition quickly and with high precision, since this is not desirable in terms of the quality of the steel material obtained from the steel.

Incidentally, there is a laser emission method as a publicly available technology that has not yet been put to practical use but can be used. The laser emission method is a technique of irradiating a laser beam to the molten steel 4, transmitting plasma light generated on the surface of the molten steel to a spectroscope via an optical fiber, and analyzing the components of the molten steel 4 by spectral analysis of the plasma light.

However, since the C emission line has a short wavelength of 193 nm, the transmittance in the optical fiber is extremely small at present, and the S / N ratio of the measured value is deteriorated. As a result, a practical level of analysis accuracy is obtained. There is a problem that can not be.

As a method for transporting and analyzing fine particles, Japanese Patent Laid-Open No.
No. 227949 describes a technique in which molten metal is generated as fine particles by blowing out an inert gas, and the fine particles are transported to a plasma emission analyzer for analysis. Japanese Patent Application Laid-Open No. 60-122355 describes a technique for generating and transporting fine particles by spark discharge.

[0013]

The molten steel being blown contains C in the molten steel and oxygen to be blown in a supersaturated state, and carbon monoxide gas (hereinafter, referred to as CO gas) from the molten steel surface.
Is released. That is, the gas phase near the molten steel surface always contains a considerable amount of CO gas. Therefore, JP
In the fine particle transport method disclosed in JP-A-122355, the CO gas near the molten steel is transported together with the fine particles.

In the method of analyzing and transporting fine particles disclosed in Japanese Patent Application Laid-Open No. 1-227949, a part of the CO gas generated from molten steel when the inert gas is jetted is also mixed with the inert gas and transported together with the fine particles. When laser emission is caused in such an atmosphere, not only the molten steel but also the gas near the molten steel surface is excited and emitted together, so that the emission of C in the molten steel and the emission of C from the CO gas are measured together. .

As described above, the conventional analysis method cannot accurately measure C in the molten steel due to the influence of the CO gas released from the molten steel. In particular, there is a problem of accurately measuring the C content. Therefore, the present invention provides an analysis method for accurately and quickly analyzing the C content of molten steel in a state where the influence of CO gas is excluded.

[0016]

SUMMARY OF THE INVENTION The present invention provides a method for irradiating a molten steel with a laser to vaporize a part of the molten steel into fine particles, transport the fine particles to a cell with an inert gas, and transport the fine particles and a CO gas in the cell. After separating the gas from the gas, the fine particles are conveyed to an analyzer, and the fine particles are irradiated with a laser beam to analyze a molten steel component. The above-described analysis method can be effectively applied particularly to C among molten steel components.

Further, the apparatus of the present invention comprises a laser for generating fine particles for irradiating the surface of molten steel, a condensing lens for condensing the laser and irradiating the surface of the molten steel, and a device for transporting the fine particles of molten steel generated by the laser irradiation. And a probe connected to a gas exhaust pipe for carrying out the sampled gas containing the molten steel particles to a cell.

The laser for generating fine particles, the condensing lens, and the probes connected to the gas inflow pipe and the gas discharge pipe can be inserted into the converter furnace.
The laser analyzer for analyzing molten steel described above can be mounted on the tip inside the sublance.

The above-mentioned cell is provided with a transfer pipe for introducing the above-mentioned gas collected from molten steel irradiated by the laser,
a gas supply pipe for introducing the r gas, and a suction pipe for sucking the sampled gas, which is substantially cylindrical and connected to the cell for capturing fine particles in the sampled gas. A filter disposed substantially perpendicular to the axial direction of the filter, an Ar ejection nozzle for blowing Ar gas to remove CO gas from the vicinity of the fine particles captured by the filter and float the fine particles, And a transfer pipe to the analyzer for transferring the fine particles to the plasma analyzer.

[0020]

FIG. 1 shows an outline of the configuration of the present invention. FIG. 2 shows the configuration of a cell for separating fine particles and CO gas. Probe 3 mounted on water-cooled sublance 11
Into the furnace through a furnace port (not shown),
The laser beam emitted from the fine particle generation laser 1 is brought close to the surface of the molten steel by the
To irradiate the molten steel surface.

A quartz glass 21 is attached to the probe 3 to block the inside and outside air while passing the laser beam. Probe 3
Is provided with a gas inlet pipe 5 and a gas outlet pipe 6. Inert gas enters the probe 3 through the gas inlet pipe 5,
Gas exhaust pipe 6 together with the CO gas diffused from the molten steel 4 into the probe space from the molten steel 4 by the laser irradiation.
To the cell 8.

An inorganic filter 82 is attached to the cell 8. After a gas containing fine particles flows for a certain period of time, the gas is switched to a gas containing no CO gas as a cleaning operation, and the gas is passed from the vicinity of the fine particles deposited on the filter 82. CO gas is separated and removed. After the cleaning operation for separating and removing the particles, Ar particles are blown or flowed back to the filter 82 to suspend the particles, and the particles are conveyed to the plasma analyzer 9 for C analysis of the particles.

[0023]

EXAMPLE A single mode light of a semiconductor-pumped solid-state laser was applied to molten steel 4 at 1600 ° C. under the conditions of an average pulse energy of 0.2 mJ, a pulse width of 20 nsec, and a pulse frequency of 50 kHz.
Irradiation was performed through an optical system having a beam expander of 10 times and a condenser lens of 200 mm. The probe is made of boron nitride, flows Ar gas at a flow rate of 2 l / min, and has an inner diameter of 4 mm.
With a φ stainless steel transfer tube, the fine particles are transferred about 10 m,
Led to the cell.

The fine particles are collected by an alumina filter 82 having a pore diameter of 0.1 μm in the cell 8 for 5 seconds.
After being replaced by an Ar gas flow of 5 l / min for 5 seconds thereafter, 1 l of the air was discharged from the Ar ejection nozzle 87 having a narrowed tip.
Ar gas is blown onto the filter 82 at a flow rate of / min,
The fine particles adhered to the filter 82 were separated and floated, and were conveyed to the plasma of the inductively coupled plasma analyzer 9 to emit and emit light.

The excited light was dispersed into a spectrum of C and iron by a spectroscope, and the intensity was measured by a photodetector. The measurement wavelength C was 193 nm, and iron was 271 nm. At the same time, Mn, which is also an important element, was changed to 293.
nm, P at 178 nm and S at 183 nm.

A calibration curve for converting the spectral intensity into a concentration was prepared by irradiating a laser to a steel standard sample having a known content to generate fine particles, and collecting and emitting the fine particles. One of the advantages of the present invention is that the calibration curve is accurate because the composition of the fine particles does not depend on the form before generation.

FIG. 3 shows the relationship between the C content in the molten steel according to the present invention and the C emission intensity of the produced fine particles, and FIG. 4 shows the C content in the molten steel when the CO gas is not separated by the conventional fine particle transport method. The relationship of the C emission intensity of the produced fine particles is shown. When the CO gas was not separated, there was no correlation between the C content in the molten steel and the C emission intensity, but a high correlation was obtained in the present invention, and the C content in the molten steel was determined from the C emission intensity of the fine particles.

[0028]

According to the present invention, the C content of molten steel during blowing in a converter or the like can be measured quickly and accurately, and the analysis waiting time is not required. Also, after blowing,
Improve steelmaking efficiency by eliminating the need for a “post-blowing” process to correct errors in analysis results, reduce steelmaking costs by reducing damage to refractories such as furnace walls, and manufacture according to production plans. The reduction of the loss is achieved, and the effect of the present invention on the steelmaking operation is extremely large.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a configuration of the present invention.

FIG. 2 is a diagram showing a configuration of a cell for separating fine particles and CO gas.

FIG. 3 is a diagram showing the relationship between the C content in molten steel and the C emission intensity of produced fine particles according to the present invention.

FIG. 4 is a diagram showing the relationship between the C content in molten steel and the C emission intensity of generated fine particles when CO gas is not separated according to a conventional fine particle transport method.

FIG. 5 is a diagram illustrating a method of analyzing molten steel in a conventional converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Particle generation laser 2 Condensing lens 3 Probe 4 Molten steel 5 Gas inflow pipe 6 Gas exhaust pipe 7 Carrier pipe 8 Cell 9 Plasma analyzer 11 Sublance 21 Quartz glass 40 Converter 41 Slag 43 Oxygen lance 82 Filter 84 Ar air supply pipe 85 Suction pipe 86 Transport pipe to analyzer 87 Ar jet nozzle 88 Electromagnetic valve

Claims (5)

[Claims] 1. A method for irradiating a laser beam on molten steel to vaporize a part of the molten steel to form fine particles, transport the fine particles to a cell with an inert gas, and separate the fine particles from a carrier gas containing a CO gas in the cell.
A rapid analysis method for molten steel that transports and analyzes fine particles to an analyzer. 2. The method according to claim 1, wherein the composition of the molten steel is carbon. 3. A laser for generating fine particles for irradiating the surface of molten steel, a condenser lens for condensing the laser and irradiating the surface of the molten steel, and a gas for flowing a gas for conveying the fine particles of molten steel generated by the laser irradiation. A laser analyzer for analyzing molten steel, comprising: an inflow pipe and a probe connected to a gas exhaust pipe for carrying out a sampled gas containing the molten steel particles to a cell. 4. A sub-lance inside a sub-lance so that the laser for generating fine particles, the condenser lens, and a probe connected to the gas inlet pipe and the gas outlet pipe can be inserted into the converter furnace. The laser analyzer for molten steel analysis according to claim 3, wherein the laser analyzer is attached to a tip of the steel plate. 5. A transport pipe for introducing the sampled gas collected from the molten steel irradiated by the laser, an air supply pipe for introducing an Ar gas, and a suction pipe for sucking the sampled gas. A connected substantially cylindrical cell, wherein a filter disposed in the cell in a direction substantially perpendicular to the axial direction of the cell for capturing fine particles in the collected gas; An Ar ejection nozzle for blowing Ar gas for removing CO gas from the vicinity of the fine particles and suspending the fine particles, and a transport pipe to an analyzer for transporting the suspended fine particles to a plasma analyzer, A cell comprising: